Stacked type semiconductor memory device

ABSTRACT

According to one embodiment, a semiconductor memory device includes a stacked body which is provided on a substrate and in which an insulating film and an electrode film are alternately stacked. The semiconductor memory device also includes an insulating member which penetrates the stacked body in a stacking direction of the insulating film and the electrode film to thereby separate the stacked body. The semiconductor memory device also includes a semiconductor pillar which penetrates the stacked body in the stacking direction. A maximum portion of the insulating member where a first distance from a side surface of the insulating member to a central plane of the insulating member becomes maximum and a maximum portion of the semiconductor pillar where a second distance from a side surface of the semiconductor pillar to a center line of the semiconductor pillar becomes maximum being provided in different positions in the stacking direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/629,193 filed Jun. 21, 2017, which is a Continuation of U.S.application Ser. No. 14/645,672 filed Mar. 12, 2015, which is based uponand claims the benefit of priority from U.S. Provisional PatentApplication 62/047,835, filed on Sep. 9, 2014; the entire contents ofeach of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor memorydevice and a method for manufacturing the same.

BACKGROUND

Although conventionally, high integration of a semiconductor memorydevice is being promoted, a method for increasing the degree ofintegration by the enhancement of lithography and etching technologiesis getting closer to its limit, and a stacked-type semiconductor memorydevice is proposed. In this stacked-type semiconductor memory device, astacked body in which word lines and interlayer insulating films arealternately stacked and a silicon pillar penetrating the stacked bodyare provided. A slit for separating the word line is formed in thestacked body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a semiconductor memorydevice according to a first embodiment;

FIG. 2 is a cross-sectional view illustrating a slit and a memory holeof the semiconductor memory device according to the first embodiment;

FIGS. 3 to 17 are cross-sectional views illustrating the method formanufacturing the semiconductor memory device according to the firstembodiment;

FIG. 18 is a cross-sectional view illustrating a semiconductor memorydevice according to a variation of the first embodiment;

FIG. 19 is a cross-sectional view illustrating a semiconductor memorydevice according to a second embodiment;

FIGS. 20 to 25 are cross-sectional views illustrating the method formanufacturing the semiconductor memory device according to the secondembodiment; and

FIG. 26 is a cross-sectional view illustrating a semiconductor memorydevice according to a variation of the second embodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor memory device includes asubstrate. The semiconductor memory device also includes a stacked bodywhich is provided on the substrate and in which an insulating film andan electrode film are alternately stacked. The semiconductor memorydevice also includes an insulating member which penetrates the stackedbody in a stacking direction of the insulating film and the electrodefilm to thereby separate the stacked body. The semiconductor memorydevice also includes a semiconductor pillar which penetrates the stackedbody in the stacking direction. A maximum portion of the insulatingmember where a first distance from a side surface of the insulatingmember to a central plane of the insulating member becomes maximum and amaximum portion of the semiconductor pillar where a second distance froma side surface of the semiconductor pillar to a center line of thesemiconductor pillar becomes maximum being provided in differentpositions in the stacking direction.

According to one embodiment, a method for manufacturing a semiconductormemory device includes a step of stacking a first insulating film and afirst electrode film alternately on a substrate to thereby form a firststacked body, forming a first slit penetrating the first stacked body ina stacking direction of the first insulating film and the firstelectrode film and forming a filling film within the first slit tothereby form a first structure member. The method for manufacturing asemiconductor memory device also includes a step of stacking a secondinsulating film and a second electrode film on the first structuremember to thereby form a second stacked body. The method formanufacturing a semiconductor memory device also includes a step offorming on a side of the first slit, a memory hole penetrating the firststacked body and the second stacked body in the stacking direction. Themethod for manufacturing a semiconductor memory device also includes astep of forming a memory film on a side surface of the memory hole tothereby form a semiconductor pillar within the memory hole. The methodfor manufacturing a semiconductor memory device also includes a step offorming, immediately above the first slit, a second slit penetrating thesecond stacked body in the stacking direction. The method formanufacturing a semiconductor memory device also includes a step ofremoving the filing film within the first slit and filling the firstslit and the second slit with an insulating material to thereby form aninsulating member.

Hereinafter, embodiments of the invention will be described withreference to the drawings.

First Embodiment

First, a first embodiment will first be described.

FIG. 1 is a cross-sectional view illustrating a semiconductor memorydevice according to the embodiment.

FIG. 2 is a cross-sectional view illustrating a slit and a memory holeof the semiconductor memory device according to the embodiment.

The semiconductor memory device according to the embodiment is astacked-type semiconductor memory device.

As shown in FIG. 1, in the semiconductor memory device 1 according tothe embodiment, a silicon substrate 10 is provided in the lowermostlayer, and an insulating film 11 is provided on the silicon substrate10.

Hereinafter, in the following specification, for convenience ofexplanation, an XYZ orthogonal coordinate system will be adopted.Namely, in FIG. 1, two directions parallel to a contact face of thesilicon substrate 10 and the insulating film 11 and orthogonal to eachother are assumed to be an “X-direction” and a “Y-direction”. An upwarddirection perpendicular to the contact face of the silicon substrate 10and the insulating film 11 is assumed to be a “Z-direction”.

A back gate electrode BG, a stopper film 14, a stacked body 13, aninterlayer insulating film 36, a selection gate electrode SG, aninterlayer insulating film 37, an interlayer insulating film 38, aninterlayer insulating film 39, a source line SL and a bit line BL, frombelow along the Z-direction, are provided on the insulating film 11 ofthe semiconductor memory device 1. The stacked body 13 is formed byalternately and repeatedly stacking an interlayer insulating film 12 anda word line WL.

A lower portion 25 of the slit ST for separating the word line WL isformed on the stopper film 14 so as to penetrate the stacked body 13 inthe Z-direction. An upper portion 42 of the slit ST is formed on thelower portion 25 of the slit ST so as to penetrate the stacked body inthe Z-direction from the interlayer insulating film 37 to the interlayerinsulating film 36. An insulating member 22 formed of an insulatingmaterial is provided within the lower portion 25 of the slit ST and theupper portion 42 of the slit ST. The insulating member 22 extends in theY-direction.

The memory holes MH are formed on the insulating film 11 so as topenetrate the stacked body in the Z-direction from the interlayerinsulating film 37 to the upper layer portion of the back gate electrodeBG. The lower end of each of a pair of memory holes MH is connected to ajoint portion JP that is provided within the back gate electrode BG andthat extends in the X-direction. The pair of memory holes MH and thejoint portion JP are formed in the shape of the letter U.

A memory film 15 is provided on the side surface of the pair of memoryholes MH and the joint portion JP. A silicon pillar SP is provided onthe side of a center axis of the memory film 15. In this way, thesilicon pillar SP is formed in the shape of the letter U. In the memoryfilm 15, a block insulating film, a charge film and a tunnel insulatingfilm are stacked and formed sequentially from the outside. In this way,a memory cell is formed in a portion where the word line WL and thesilicon pillar SP intersect each other.

A contact plug CP_(SL) embedded into the interlayer insulating film 38is provided on one end of the silicon pillar SP in the shape of theletter U. The source line SL embedded into the interlayer insulatingfilm 39 and extending in the Y-direction is provided on the contact plugCP_(SL). A contact plug CP_(BL) embedded into the interlayer insulatingfilm 38 and the interlayer insulating film 39 is provided on the otherend of the silicon pillar SP. The bit line BL extending in theX-direction is provided on the contact plug CP_(BL) and the interlayerinsulating film 39.

The insulating film 11 and the interlayer insulating films 12 and 36 to39 are formed of, for example, silicon oxide (SiO). The back gateelectrode BG, the word line WL and the selection gate electrode SG areformed of, for example, silicon (Si) and a metal silicide containingboron (B). The stopper film 14 is formed of, for example, tantalum (Ta).The contact plug CP_(SL), the contact plug CP_(BL), the source line SLand the bit line BL are formed of, for example, tungsten (W).

Each of the cross-sectional shapes of the lower portion 22 a of theinsulating member 22, the upper portion 22 b of the insulating member 22and the silicon pillar SP is formed as shown in FIG. 2 because of a highprocessing aspect. This shape is characterized in that its part slightlyswells in a position slightly away from the upper end. This shape isreferred to as a bowing shape. A portion where the distance R from theside wall of the slit to a center line P of the slit is maximized isreferred to as a maximum bowing portion Z.

Since the position of the upper end of the silicon pillar SP and theposition of the upper end of the lower portion 22 a of the insulatingmember 22 are different from each other, the position of the maximumbowing portion Z_(MH) of the silicon pillar SP and the maximum bowingportion Z_(ST1) of the lower portion 22 a of the insulating member 22are displaced in the Z-direction. A minimum point where the distancefrom the side wall of the insulating member 22 to the central planebecomes minimum is Z_(ST21) as shown in FIG. 1.

Furthermore, although the position of the upper end of the siliconpillar SP and the position of the upper end of the upper portion 22 b ofthe insulating member 22 are located in the position of the same height,since their lengths are different, the position of the maximum bowingportion Z_(MH) of the silicon pillar SP and the position of the maximumbowing portion Z_(ST2) of the upper portion 22 b of the insulatingmember 22 are displaced in the Z-direction. Moreover, since the lengthof the upper portion 22 b in the Z-direction is shorter than the lengthof the lower portion 22 a and the length of the silicon pillar SP, thewidth of the maximum bowing portion Z_(ST2) of the upper portion 22 b isless than that of the lower portion 22 a and the silicon pillar SP.

Next, a method for manufacturing the semiconductor memory deviceaccording to the embodiment will be explained.

FIGS. 3 to 17 are cross-sectional views illustrating the method formanufacturing the semiconductor memory device according to theembodiment.

First, as shown in FIG. 3, the insulating film 11 made of silicon oxide(SiO) is formed on the silicon substrate 10 by, for example, HDP-CVD(High Density Plasma Chemical Vapor Deposition), and the back gateelectrode BG is formed thereon. Thereafter, the range of formation of agroove 33 is identified by lithography, and etching is performed toselectively remove the back gate electrode BG and to form the groove 33.Thereafter, a sacrificial film 34 is formed within the groove 33 by, forexample, deposition of non-doped silicon. The “non-doped” refers to thefact that an impurity for giving conductivity to silicon is notintentionally added and that no impurities are substantially includedexcept for an element caused by a raw gas at the time of film formation.Thereafter, a stopper film 14 is formed on the back gate electrode BGand the sacrificial film 34 by deposition of, for example, tantalum(Ta).

Next, as shown in FIG. 4, the stacked body 13 is formed by alternatelydepositing, on the stopper film 14, the interlayer insulating film 12and the word line WL.

Subsequently, as shown in FIG. 5, the range of formation of the lowerportion 25 of the slit ST is identified by, for example, lithography,the interlayer insulating film 12 and the word line WL are selectivelyremoved by performing etching, and thus the lower portion 25 of the slitST penetrating the stacked body 13 in the Z-direction and extending inthe Y-direction is formed. In this way, the word line WL is separated inthe X-direction. At this time, the cross-sectional shape of the lowerportion 25 of the slit ST becomes a shape shown in FIG. 2 because of ahigh aspect ratio.

Namely, as described above, as shown in FIG. 2, the cross-sectionalshape of the slit ST becomes a bowing shape where its part slightlyswells in a position slightly away from the upper end of the slit ST.For example, when a slit is formed in a stacked body made of a word lineand an interlayer insulating film and having a thickness of 1.5 μm, themaximum bowing portion Z is located approximately 300 nm away from theupper end of the slit.

Then, as shown in FIG. 6, a filling film 18 is formed by embedding amaterial made of, for example, amorphous silicon (aSi), silicon nitride(SiO), silicon oxide (SiN) or the like, into the lower portion 25 of theslit ST.

After that, as shown in FIG. 7, the interlayer insulating film 36, theselection gate electrode SG and the interlayer insulating film 37 arestacked in this order on the stacked body 13 and the filling film 18.

Subsequently, as shown in FIG. 8, the range of formation of the memoryhole MH is identified by lithography, the stacked body from theinterlayer insulating film 37 to the stopper film 14 is selectivelyremoved by performing etching and thus the memory hole MH penetratingthis stacked body in the Z-direction is formed. At this time, thecross-section shape of the memory hole MH becomes a bowing shape in thesame way as the lower portion 25 of the slit ST because of a high aspectratio. However, since the position T₁ of the upper end of the memoryhole MH is higher than the position T₂ of the upper end of the lowerportion 25, as indicated by a part A in FIG. 8, the position of themaximum bowing portion Z_(MH) of the memory hole MH can be set higherthan the position of the maximum bowing portion Z_(ST1) of the lowerportion 25.

The lower end of the memory hole MH reaches the sacrificial film 34, andthe sacrificial film 34 is exposed to the lower end of the memory holeMH. A pair of memory holes MH is formed on one sacrificial film 34 so asto sandwich the insulating member 18. After that, the sacrificial film34 of non-doped silicon is removed by, for example, wet etching.

The groove 33 formed within the back gate electrode BG emerges by theremoval of the sacrificial film 34. The groove 33 that emerges isreferred to as the joint portion JP. A pair of the memory holes MH isconnected to one joint portion JP. The lower end of each of the pair ofthe memory holes MH is connected to one common joint portion JP and onecavity in the shape of the letter U is formed.

Next, as shown in FIG. 9, a block insulating film, a charge film and atunnel insulating film are formed in this order on the side surface ofthe pair of the memory holes MH and the joint portion JP, and thus thememory film 15 is formed. Thereafter, the silicon pillar SP is formed byembedding the pair of the memory holes MH and the joint portion JP byusing, for example, silicon.

Then, as shown in FIG. 10, the range of formation of the upper portion42 of the slit ST is identified by lithography, the stacked body fromthe interlayer insulating film 37 and the interlayer insulating film 36is selectively removed by performing etching and thus the upper portion42 of the slit ST penetrating the stacked body in the Z-direction andextending in the Y-direction is formed. The central plane of the upperportion 42 of the slit ST is aligned with the central plane of the lowerportion 25 of the slit ST. At this time, the cross-sectional shape ofthe upper portion 42 of the slit ST becomes a bowing shape because of ahigh aspect ratio. After that, the position of the upper end of thememory hole MH and the position of the upper end of the upper portion 42are located in the position T₁ of the same height. However, since theirlengths are different from each other, as indicated by a part B in FIG.10, the position Z_(MH1) of the maximum bowing portion of the memoryhole MH and the position Z_(ST2) of the maximum bowing portion of theupper portion 42 can be displaced in the Z-direction. Furthermore, sincethe length of the upper portion 42 in the Z-direction is shorter thanthe length of the lower portion 25 and the length of the memory hole MH,the width of the maximum bowing portion Z_(ST2) of the upper portion 42is less than that of the lower portion 25 and the memory hole MH.

Subsequently, as shown in FIG. 11, the filling film 18 is removed byperforming etching on the filling film 18 within the lower portion 25 ofthe slit ST, with the result that the desired shape of the lower portion25 of the slit ST is obtained.

Next, as shown in FIG. 12, a metal film 21 is formed by depositing ametal such as nickel (Ni) or cobalt (Co) within the slit ST and asilicide (not shown) is formed by reaction with the silicon of the wordline WL.

Then, as shown in FIG. 13, an unreacted part of the metal film 21 isremoved. After that, the insulating member 22 is formed by embedding aninsulating material into the slit ST.

Subsequently, as shown in FIG. 14, a contact hole 41 is formed byforming the interlayer insulating film 38 on the interlayer insulatingfilm 37 to thereby form a flat face, and then by performing lithographyand etching. Thereafter, a conductive film 43 is formed by depositing,for example, tungsten (W) on the interlayer insulating film 38 and thecontact hole 41.

Then, as shown in FIG. 15, a contact plug CP_(SL) is formed within thecontact hole 41 by removing the conductive film 43 formed on the upperface of the interlayer insulating film 38 through, for example, a CMPmethod.

Next, as shown in FIG. 16, the source line SL extending in theY-direction is formed on the contact plug CP_(SL) by, for example, adamascene method.

Then, as shown in FIG. 17, a contact hole 44 is formed by formation ofthe interlayer insulating film 39 on the interlayer insulating film 38and the source line SL, and then by performing lithography and etching.Thereafter, a contact plug CP_(BL) is formed by the same method as themethod for forming the contact plug CP_(SL).

After that, as shown in FIG. 1, the bit line BL extending in theX-direction is formed on the contact plug CP_(BL) by, for example, thedamascene method, and thus the semiconductor memory device 1 ismanufactured.

Subsequently, the effects of the embodiment will be described.

In the semiconductor memory device according to the embodiment, theposition of the upper end of the silicon pillar SP is caused to differfrom the position of the upper end of the lower portion 22 a of theinsulating member 22, and thus it is possible to displace, in theZ-direction, the position of the maximum bowing portion Z_(MH) of thesilicon pillar SP and the position of the maximum bowing portion Z_(ST1)of the lower portion 22 a of the insulating member 22. Furthermore, theposition of the upper end of the silicon pillar SP and the position ofthe upper end of the upper portion 22 b of the insulating member 22 arelocated at the same height, but since their lengths are different fromeach other, it is possible to displace, in the Z-direction, the positionof the maximum bowing portion Z_(MH) of the silicon pillar SP and theposition of the maximum bowing portion Z_(ST2) of the upper portion 22 bof the insulating member 22. Furthermore, since the length of the upperportion 22 b in the Z-direction is shorter than the length of the lowerportion 22 a and the length of the silicon pillar SP, the width of themaximum bowing portion Z_(ST2) of the upper portion 22 b is less thanthat of the lower portion 22 a and the silicon pillar SP.

As a result, the minimum distance between the silicon pillar SP and theinsulating member 22 is increased, and thus it is possible to preventthe silicon pillar SP and the insulating member 22 from beingexcessively close to each other. Since the minimum cross-sectional areaof the word line WL sandwiched between the silicon pillar SP and theinsulating member 22 on the XZ plane can be acquired so as to be notless than a prescribed value, it is possible to lower the wiringresistance of the word line WL.

Although in the embodiment, the example has been described in which thelower portion 25 of the slit ST is formed, then the memory hole MH isformed and thereafter the upper portion 42 of the slit ST is formed,there is no restriction on this example. There may be adopted aconfiguration in which the upper portion 42 of the slit ST is formedafter formation of the lower portion 25 of the slit ST and then, thememory hole MH is formed.

Furthermore, after separately forming the slit ST by using not less thanthree processes, the insulating member 22 may be formed by embedding aninsulating material into the slit ST.

Modification of the First Embodiment

Next, a modification of the first embodiment will be described.

FIG. 18 is a cross-sectional view illustrating a semiconductor memorydevice according to the variation.

As shown in FIG. 18, in the semiconductor memory device 1 in a case ofseparately forming the slit ST by using, for example, three processes,in the Z-direction, the position of the maximum bowing portion Z_(MH) ofthe silicon pillar SP is provided to be higher than the position of themaximum bowing portion Z_(ST2) of the insulating member 22. Furthermore,there are two points Z_(ST31) and Z_(ST32), as the minimum point wherethe distance from the side wall of the insulating member 22 to thecentral plane becomes minimum, as shown in FIG. 16.

The configurations, the manufacturing method and the effects other thanwhat has been described above in the variation are the same as in thefirst embodiment described above.

Second Embodiment

Subsequently, a second embodiment will be described.

FIG. 19 is a cross-sectional view illustrating a semiconductor memorydevice according to the embodiment.

In the semiconductor memory device 1 according to the embodiment, thememory hole MH that penetrates, in the Z-direction, the stacked bodyfrom the interlayer insulating film 37 to the upper layer portion of theback gate electrode BG is formed by being etched twice, and the slit STthat penetrates, in the Z-direction, the stacked body from theinterlayer insulating film 37 to the stacked body 13 is formed by beingetched once.

Consequently, as shown in FIG. 19, the semiconductor memory device 1according to the embodiment differs from the above-describedsemiconductor memory device (see FIG. 1) according to the firstembodiment in the following points (a) to (e).

(a) The silicon pillar SP is divided into an upper portion 47 and alower portion 46, and the cross section of each of them has the bowingshape.

(b) An insulating member 28 is not divided, and its cross section hasone bowing shape.

(c) Since the upper end of the lower portion 46 of the silicon pillar SPand the upper end of the insulating member 28 are located in differentpositions, the position of the maximum bowing portion Z_(MH1) of thelower portion 46 and the position of the maximum bowing portion Z_(ST)of the insulating member 28 are displaced in the Z-direction.

(d) The upper end of the upper portion 47 of the silicon pillar SP andthe upper end of the insulating member 28 are located in the position ofthe same height, but since their lengths are different from each other,the position of the maximum bowing portion Z_(MH2) of the upper portion47 and the position of the maximum bowing portion Z_(ST) of theinsulating member 28 are displaced in the Z-direction.

(e) A minimum point where the distance from the side wall of the siliconpillar SP to the center line becomes minimum is Z_(MH21) as shown inFIG. 19.

The configurations other than what has been described above in theembodiment are the same as in the first embodiment described above.

Then, a method for manufacturing the semiconductor memory deviceaccording to the embodiment will be described.

FIGS. 20 to 25 are cross-sectional views illustrating the method formanufacturing the semiconductor memory device according to theembodiment.

First, a method for forming the stacked body 13 on the silicon substrate10 from the beginning is the same as in the first embodiment describedabove.

After that, as shown in FIG. 20, the range of formation of the lowerportion 26 of the memory hole MH is identified by, for example,lithography, the stacked body is selectively removed from the stackedbody 13 to the upper layer portion of the back gate electrode BG byperforming etching, and thus the lower portion 26 of the memory hole MHpenetrating this stacked body in the Z-direction is formed. At thistime, the cross-sectional shape of the lower portion 26 of the memoryhole MH becomes a bowing shape because of a high aspect ratio.Thereafter, a filling film 23 is formed by embedding a material made of,for example, amorphous silicon (aSi), silicon nitride (SiO), siliconoxide (SiN) or the like into the lower portion 26 of the memory hole MH.

Next, as shown in FIG. 21, the interlayer insulating film 36, theselection gate electrode SG and the interlayer insulating film 37 arestacked in this order on the stacked body 13 and the filling film 23.

Then, as shown in FIG. 22, the range of formation of the slit ST isidentified by lithography, the stacked body is selectively removed fromthe interlayer insulating film 37 to the stacked body 13 by performingetching, and thus the slit ST penetrating this stacked body in theY-direction is formed. At this time, the cross-sectional shape of theslit ST also becomes a bowing shape in the same way as the lower portion26 of the memory hole MH because of a high aspect ratio. However, sincethe position T₁ of the upper end of the slit ST is higher than theposition T₂ of the upper end of the filling film 23, as indicated by apart C in FIG. 22, the position Z_(ST) of the maximum bowing portion ofthe slit ST can be set higher than the position Z_(MH1) of the maximumbowing portion of the filling film 23. Thereafter, a metal film 27 isformed by deposition of a metal such as nickel (Ni) or cobalt (Co)within the slit ST, and reaction with the silicon of the word line WL iscaused to form a silicide (not shown).

Then, as shown in FIG. 23, an unreacted part of the metal film 27 isremoved. Thereafter, the insulating member 28 is formed by embedding aninsulating material into the slit ST.

Then, as shown in FIG. 24, the range of formation of the upper portion45 of the memory hole MH is identified by lithography, the stacked bodyis selectively removed from the interlayer insulating film 37 to theinterlayer insulating film 36 by performing etching, and thus the upperportion 45 of the memory hole MH penetrating this stacked body in theZ-direction is formed. The center line of the upper portion 45 of thememory hole MH is aligned with the center line of the lower portion 26of the memory hole MH. At this time, the cross-sectional shape of theupper portion 45 of the memory hole MH also becomes a bowing shapebecause of a high aspect ratio. Then, the position of the upper end ofthe insulating member 28 and the position of the upper end of the upperportion 45 of the memory hole MH are located in the position T₁ of thesame height. However, since their lengths are different from each other,as indicated by a part D in FIG. 24, the position Z_(ST) of the maximumbowing portion of the insulating member 28 and the position Z_(MH2) ofthe maximum bowing portion of the upper portion 45 of the memory hole MHcan be displaced in the Z-direction. Furthermore, since the length ofthe upper portion 45 in the Z-direction is shorter than the length ofthe lower portion 26 and the length of the memory hole MH, the width ofthe maximum bowing portion Z_(MH2) of the upper portion 45 is less thanthat of the lower portion 26 and the memory hole MH.

Subsequently, as shown in FIG. 25, the filling film 23 and thesacrificial film 34 are removed by performing etching on the fillingfilm 23 within the lower portion 26 of the memory hole MH and thesacrificial film 34. The groove 33 formed within the back gate electrodeBG emerges by the removal of the sacrificial film 34. The groove 33 thatemerges is referred to as the joint portion JP. Thereafter, a blockinsulating film, a charge film and a tunnel insulating film are formedin this order on the side surface of the memory hole MH formed of thelower portion 26 and the upper portion 45 and on the side surface of thejoint portion JP and thus the memory film 21 is formed. After that, thesilicon pillar SP is formed by embedding the pair of the memory holes MHand the joint portion JP by using, for example, silicon.

A method for forming the portions from the contact plug CP_(SL) to thebit line BL is the same as in the first embodiment described above.

The manufacturing method other than what has been described above in theembodiment is the same as in the first embodiment described above.

Next, the effects of the embodiment will be described.

In the semiconductor memory device according to the embodiment, theposition of the upper end of the insulating member 28 and the positionof the upper end of the lower portion 46 of the silicon pillar SP aremade to differ from each other, and thus the position of the maximumbowing portion Z_(ST) of the insulating member 28 and the position ofthe maximum bowing portion Z_(MH1) of the lower portion 46 can bedisplaced in the Z-direction. In addition, the position of the upper endof the insulating member 28 and the position of the upper end of theupper portion 47 are located at the same height, but since their lengthsare different from each other, the position of the maximum bowingportion Z_(ST) of the insulating member 28 and the position of themaximum bowing portion Z_(MH2) of the upper portion 47 can be displacedin the Z-direction. Furthermore, since the length of the upper portion47 in the Z-direction is shorter than the length of the lower portion 46and the length of the insulating member 28, the width of the maximumbowing portion Z_(MH2) of the upper portion 47 is less than that of thelower portion 46 and the insulating member 28.

Consequently, the minimum distance between the insulating member 28 andthe silicon pillar SP is increased, and thus it is possible to preventthe insulating member 28 and the silicon pillar SP from beingexcessively close to each other. Since the minimum cross-sectional areaof the word line WL sandwiched between the insulating member 28 and thesilicon pillar SP on the XZ plane can be secured so as to be not lessthan a prescribed value, it is possible to lower the wiring resistanceof the word line WL.

Although in the embodiment, the example has been described in which thelower portion 26 of the memory hole MH is formed, then the slit ST isformed and thereafter the upper portion 45 of the memory hole MH isformed, there is no restriction on this example. There may be adopted aconfiguration in which the upper portion 45 of the memory hole MH isformed after formation of the lower portion 26 of memory hole MH andthen, the slit ST is formed.

After the memory hole MH is formed separately by using not less thanthree processes, the memory film 21 is formed on the side surface of thememory hole MH and on the side surface of the joint portion JP. Afterthat, a pair of the memory holes MH and the joint portion JP areembedded using, for example, silicon and thus the silicon pillar SP isformed.

Variation of the Second Embodiment

Next, a variation of the second embodiment will be described.

FIG. 26 is a cross-sectional view illustrating a semiconductor memorydevice according to the variation.

As shown in FIG. 26, in the semiconductor memory device 1 in a case ofseparately forming the memory hole MH by using, for example, threeprocesses, the position of the maximum bowing portion Z_(ST) of theinsulating member 28 is provided to be higher than the position of themaximum bowing portion Z_(MH2) of the silicon pillar SP, in theZ-direction. There are two points Z_(MH31) and Z_(MH32), as the minimumpoint where the distance from the side wall of the silicon pillar SP tothe center line becomes minimum as shown in FIG. 26.

The configurations, the manufacturing method and the effects other thanwhat has been described above in the variation are the same as in thesecond embodiment described above.

In the embodiments described above, it is possible to prevent thesilicon pillar and the insulating member from being excessively close toeach other and to provide a semiconductor memory device in which thewiring resistance of the word line WL is low and a method formanufacturing the same.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. A method for manufacturing a semiconductor memorydevice, comprising: forming a first stacked body including a firstinsulating film and a first electrode film alternately stacked, forminga first memory hole penetrating the first stacked body in a stackingdirection of the first stacked body and forming a filling film withinthe first memory hole to thereby form a first structure member, thefirst electrode film functioning as a word line; stacking a secondinsulating film and a second electrode film on the first structuremember to thereby form a second stacked body, the second electrode filmfunctioning as a selection gate electrode; forming, on a side of thefirst memory hole, a slit extending in the first stacked body and thesecond stacked body in the stacking direction and a first directioncrossing the stacking direction; filling the slit with an insulatingmaterial to thereby form an insulating member, the insulating memberhaving a first maximum portion, the first maximum portion having amaximum width of the insulating member along a second direction crossingthe stacking direction and the first direction, the first maximumportion being located between a top end portion of the insulating memberand a bottom end portion of the insulating member in the stackingdirection, the maximum width being greater than a width of the top endportion and a width of the bottom end portion; forming, immediatelyabove the first memory hole and on a side of the slit, a second memoryhole penetrating the second stacked body in the stacking direction; andremoving the filling film within the first memory hole, forming a memoryfilm on a side surface of the first memory hole and the second memoryhole and forming a semiconductor pillar within the first memory hole andthe second memory hole, the semiconductor pillar having a second maximumportion, the second maximum portion having a maximum diameter of thesemiconductor pillar along a plane parallel with the first direction andthe second direction, the first maximum portion and the second maximumportion being provided in different positions in the stacking direction.2. The method according to claim 1, wherein the forming the firststructure member is repeated a plurality of times.
 3. The methodaccording to claim 1, wherein the forming the first structure member isrepeated a plurality of times.
 4. The method according to claim 1,further comprising: forming a metal film within the slit; and making themetal film react with the first electrode film to form a silicide,wherein the first electrode film contains silicon.
 5. The methodaccording to claim 1, wherein the first electrode film and the secondelectrode film include silicon and boron.